Wireless systems run into the inherent limitation that there is a finite amount of spectrum available for transmitting signals. And while efforts have been made to split up the spectrum in a time-divided manner to minimize interference, the possibility of interference may remain a concern.
This is a particular problem with systems that occupy a comparatively large frequency range such as wide bandwidth and ultrawide bandwidth (UWB) systems. When a network broadcasts over a large spectrum there may be one or more narrowband interfering signals within that broadcast spectrum. Because of this interference, it may be desirable to limit the extent of transmission or reception over those interfering frequencies. In particular, on the reception side it may be desirable to avoid receiving the energy of interfering signals. While on the transmission side it may be desirable, or even mandated by law, to avoid transmitting signals that will interfere with certain narrowband networks.
By way of example, the current rules set forth by the Federal Communications Commission (FCC) allow for UWB networks to transmit in the spectrum from 3.1 to 10.6 GHz. This spectrum includes other signals (e.g., from cell-phone systems, radar, satellite links, altimeters, etc.)
One way to avoid the interfering signals is to include one or more notch filters in the receiver or the transmitter. These filters will reduce a frequency band from the transmitted or received signals, so that the energy transmitted or received over those bands is significantly lowered (depending upon the specific parameters of the notching filters used).
The particular notching frequencies used for a given device may be constant or variable. For example, if there are known interfering signals that are likely to always be present, or for which transmission interference must always be avoided, a notching device may be pre-programmed to provide a frequency notch at that known notch frequency. However, if the precise frequencies of interfering signals are unknown or intermittent in nature, it may be desirable to provide a notch filter that can have its filtering parameters dynamically changed to meet varying needs.
However, in an electronic device, every bit of space is precious. The inclusion of one or more notching elements will generally increase the size and cost of a device by requiring additional circuitry and using up valuable space on an integrated circuit (IC). It would therefore be desirable to provide a notching element that minimized the amount of additional circuitry required and did not take up significant space in an IC.